BMS-188667 (CTLA4Ig) represents a new class of agent that targets the blockade of the second signal in T cell activation. It has been studied in man in 3 Phase I protocols with acceptable toxicity and some efficacy in the treatment of psoriasis. This study was designed to assess the biologic activity of chronic intermittent administration of BMS-18667 in patients with psoriasis vulgaris. A major goal was to select the optimum dosing schedule. Three dosage levels (8.0, 16.0, 25.0 mg/kg were administered in 2 dosage schedules.